The pointing-cord is shifted to some notch on the _pointing-board_, to the right or left, until the shell falls at the desired point. 13. Describe the pointing-board. This is a piece of wood one foot long, two or three inches wide, and one inch thick, having a notch cut in the middle of one side, to fit on the stake and which is graduated into equal divisions from its middle. When not in use, the pointing-cord may be wound on it. [Sidenote: 59]] 14. Describe another mode of planting the _pointing-stakes_. The mortar being placed upon the middle of the platform, the gunner mounts upon it, and suspends the plummet in front of the muzzle, covering the object. Where the plummet thus suspended cuts the crest of the epaulment, the first stake is driven. A second stake is then driven in the same line between the mortar and the epaulment. The pointing-cord being attached to the first stake and stretched to the rear, over the point where the plummet touches the top of the mortar, determines the point on the ground at which the rear stake is driven. The first stake is then removed, and the cord attached permanently to the second stake. When the object cannot be seen from the mortar, owing to the interposition of some obstacle, as a parapet or a hill, two persons in sight of each other, one of whom can see the mortar, and the other the object, must by successive changes of position, place themselves in the vertical plane of fire, and at the points thus determined, stakes must be driven, one of which will serve as the object. 15. How may precision of fire be secured at night with mortars? The _direction_ is preserved by nailing or screwing two boards to the platform outside of the cheeks; the _elevation_ is marked on the quoin, or the quoin may be nailed in the proper position. [Sidenote: 60]] PART III. CHARGES. 1. What is the charge of a piece of artillery? The powder with which it is loaded. 2. What is the ordinary service charge of powder for heavy guns? _One-fourth_ the weight of the shot. 3. What is it for firing _double shot_? _One-sixth_ the weight of one shot. 4. What is the breaching charge? _One-third_ the weight of the shot. 5. What kind of charges are used in hot shot firing? Small charges from _one-fourth_ to _one-sixth_ the weight of the ball. 6. For what reason? Because balls fired with small velocities split the wood in a manner which is favorable to its burning; with a great velocity the hole closes, the ball sinks deep, and, deprived of air, chars without setting fire to the surrounding wood. 7. To what depth should hot shot penetrate? Not deeper than ten or twelve inches. 8. In ricochet firing, what kind of charges are used? Light charges generally; varying from _two-thirds_ to _one-eighth_ of the ordinary charge. [Sidenote: 61]] 9. In what manner are the charges of mortars regulated?